Just one bad night of sleep makes it more likely that employees who already displayed unwanted behaviour one day at work will display a similar type of behaviour the following day, according to a study at Rotterdam School of Management, Erasmus University (RSM). Once an employee engages in unwanted behaviour in the workplace, such as taking longer breaks than allowed, leaving early without permission, or even stealing, it might be hard to step away from it. And that is a costly affair: such behaviour is estimated to cause companies up to $200 billion per year in the USA alone.

“Unwanted behaviour in the workplace often stems from selfish impulses that are not kept in check by self-control,” says researcher Laura M. Giurge. This negative effect of impaired sleep quality is especially strong among people with a so-called ‘low moral identity’, she discovered.

Giurge went on to say: “Going home early without telling the boss is an urge most people will feel occasionally, but do not give into every time. And when people do, they often feel remorse afterwards and try to do better next time. It is known that this ability to regulate our impulses can be undermined by having had a bad night – not necessarily just by the amount of sleep, but also by impaired sleep quality.”

For this study, a group of working professionals was asked to indicate how well they had slept each day for ten consecutive working days. They were also invited to rate the extent to which they engaged in unwanted behaviour. For example, had they taken a longer lunch break than allowed that day, or had they been rude towards a co-worker?

Analyses showed that, in general, the quality of sleep the night before can indeed influence the next day’s behaviour. Those who had engaged in unwanted behaviour one day were more likely to engage in unwanted behaviour again the next day, particularly if they slept badly during the night connecting the two days.

“This study shows that the display of unwanted behaviour is not a fixed character trait,” says Giurge. “It can vary from day to day, even within the same person. Whatever the reason for starting it, a night of poor sleep can make it harder for someone to stop doing it, especially among people with a low moral identity.”

She added: “Tiredness apparently can make it harder for people to overcome the feeling that they have failed at being a good and moral person and, as a result, do not try again the next day. This can lead into a possibly destructive cycle that could help explain why unethical behaviour is so persistent in some organisations.”